<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <link rel="stylesheet" type="text/css" href="/assets/css/reset.css" />
    <link rel="stylesheet" type="text/css" href="/assets/css/first.css" />
    <link rel="stylesheet" type="text/css" href="/assets/css/index.css" />
    <style>
      iframe{
        height: calc(100% - 80px);
        width: 100%;
        margin-top: 80px;
      }
    </style>
  </head>

  <body>
    <iframe src="/content" frameborder="0"></iframe>
  </body>
</html>